The present invention relates to a device and a method for the treatment of strongly contaminated and nasty smelling media, and whenever applicable, treatment of media with very high contents of bacteria. The invention also relates to the products obtained when performing the method.
In many fields nasty smelling and strongly contaminated media are produced. In the field of animal breeding manure is produced which releases large amounts of ammonia, which constitutes an environmental drawback for the near surroundings, but also for the environment as a whole. The bacteria contents can also be high, and direct contact with the manure can be extremely hazardous to the health.
Waste water arriving at sewage treatment plants in the form of a sludge having a high content of bacteria is also highly nasty smelling and must be taken care of in an environmentally friendly way. In larger sewage treatment plants sludge has traditionally been taken care of for the digestion thereof, in order to extract gas and killed bacteria, however, this is a laborious operation requiring large plants and much time. For smaller sewage treatment plants it is common to transport the sludge to plants having a treatment facility. It is also common to deposit the sludge at waste stations.
Regarding manure it is desirable to prevent ammonium from being released in the form of ammonia. This can be achieved by oxygenating the manure thereby producing a conversion of NH4+-ions to NO3xe2x88x92-ions. One way of achieving this is to blow air through the medium by using compressors. However, this method is inefficient. The energy consumption is considerable and therefore the cost becomes high.
The sanitation aspect, i.e. the elimination of E. Coli from waste sludge and water has become increasingly important, and is to a great extent a problem.
A previously known device intended for the oxygenating of water having relatively low concentrations of solid compounds, i.e. not a sludge, is known from SE-460 706 and SE-500 416 respectively.
Canadian patent 1101138 discloses submerged turbine aeration apparatus. It comprises a hollow rotatable shaft, an intake for gas near the top end of the shaft, an outlet for gas near the bottom end of the shaft, and an impeller connected to the shaft. The impeller comprises two spaced-apart discs with a plurality of vane elements therebetween and an intake for liquid comprising an aperture adjacent the shaft for admitting the liquid. The impeller draws liquid through the aperture past the gas outlet, for mixing the liquid with the gas, and expels the liquid outwardly from the vane elements as the impeller rotates.
Although this device is usable for aeration of liquids, it cannot generate very high vortexes inside the impeller, because there is simply not enough space available.
Other examples of devices intended for oxygenating of liquids in various connections are known from e.g. U.S. Pat. Nos. 5,275,762; 5,045,202; 4,442,045; WO 96/09989; WO 97/18168 and FR-2 277 044.
However, none of these devices anticipates the present invention.
Thus, there is a need to more efficiently take care of strongly contaminated and nasty smelling media that are formed e.g. in sewage treatment plants, e.g. raw sludge, and in animal breeding, e.g. pigs manure. Waste products from butcheries and garden waste materials such as composting waste material need to be taken care of in an efficient way.
The object of the invention is therefore to provide systems, devices and methods to achieve this.
This object is achieved in accordance with one aspect of the invention with the device according to claim 1. With this device, that can be said to constitute complex stirrer, a very efficient oxygenation of the contaminated medium is achieved, which contributes to nitrification processes occurring very rapidly. In addition a cavitation is created in the medium, which brings about a temperature increase, which also contributes to a very high killing of bacteria.
A substantial reduction in the BOD values have been noted, and oxygenation is very efficient in relation to the energy consumption when running the apparatus according to the invention.
It has also been noted that there are no losses of nitrogen, and certain indications point to the fact that the total nitrogen contents even increases in e.g. manure material, by treating media with the device and method according to the invention. Thus, the raw material is xe2x80x9crefinedxe2x80x9d by performing the method according to the invention.
When performing the method according to the invention, which is defined in claim 9, a product is obtained in the form of a sludge which is virtually freed from bacteria, which has a certain concentration of nitrates and phosphorous, and which is particularly suitable as nutrition for forests and fields, plantations etc.
This sludge is very easy sedimentable such that supernatant with high concentrations of nitrate and a very compact sedimented rest is formed. This rest is excellent as earth improver and as a fertiliser. The supernatant can also be used for fertilising, e.g. for energy forests, nursery gardens, market gardens, city plantations etc.